What Is an Example of Parasitism in the Rainforest?

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Examples of parasitism in the rainforest include loa loa, candiru, rafflesia, leeches, and the fungus Ophiocordyceps unilateralis, among others. While rainforests only cover 5 percent of the Earth’s total land area, they are home to roughly half of the world’s species. Because of this, there are many more examples of parasites in the rainforest than just what is listed here.


Plants can be parasites as well as animals, and no parasitic plant is more famous than the rafflesia. Discovered in 1818 in the rainforests of Sumatra, the rafflesia has the largest flower in the world, which can weigh up to 15 pounds. It has no visible roots or leaves and is not capable of drawing energy from the sun through photosynthesis like other plants. Instead, it lives inside a jungle vine and extends its flower outside of its host only to attract insects to pollinate it. To do this, the rafflesia mimics a dead animal. Its flower is a flesh-like red color, and it smells like a decaying body. Unlike other plants, it also can generate heat, which helps it resemble a freshly killed animal. Because of these traits, the rafflesia is also known as a corpse flower.

Land Leeches

Leeches live on every continent except Antarctica, and even then, they can still be found in the Antarctic Ocean. Although leeches have a reputation for being bloodsuckers, most have no interest in humans. However, land leeches, which live in the jungles of Madagascar, Indonesia, India, are a different story. While other leeches hunt for their prey in water, land leeches lie in wait on the jungle floor, waiting for prey to approach. They wave their heads to detect disturbances in their environment with their chemoreceptors, and they can bite through clothing should they happen upon a human. Once they find their victim, they bite through skin to draw blood, which they can store inside themselves for months.

Loa Loa

Also known as an African eye worm, the loa loa is a nematode that infects humans through deerfly bites in swamps and rainforests in West Africa and Central Africa. These worms move beneath the skin and through the bloodstream during the day. Should the loa loa hold still long enough, it will leave a visible, worm-shaped welt on the skin called a calabar swelling. At night, the loa loa retreats to the lungs. Adult worms have also been known to live in human eyes, where they are also visible and can be removed safely. 


Also known as a vampire or toothpick fish, the candiru lives in rainforest rivers throughout much of South America. This small, thin fish survives by entering the gills of fish and pinning itself in place with its spines. Once positioned, it drinks the blood of its host. 

European explorers thought that the candiru was attracted by urine and would attempt to enter the urethras of unfortunate humans bathing in the water. However, exception for one controversial sighting in 1997, there is no record of candiru ever attempting to use humans as hosts. 

Ophiocordyceps unilateralis

This difficult-to-pronounce fungus can be found in the forests of Brazil, where it infects the brains of carpenter ants. Once infected, the ants begin to act strangely before eventually climbing up the north side of a plant. Once there, they bite a leaf vein, and the fungus begins to reproduce. The ant’s mandibles lock in place around the leaf while the rest of it thrashes in place until it dies. The fungus sprouts out the back of the ant’s head until it can attach itself to the plant, at which point it releases spores to infect more ants and begin the process again.